Update README.md

Author: lrytz

README.md

@@ -34,9 +34,9 @@ sbt> compilation/jmh:run -help
 compilation/jmh:run (Cold|Warm|Hot)CompilationBenchmark 
    -p source=(<subdir of corpus>|/path/to/src/dir|@/path/to/argsfile)
    -p extraArgs=-nowarn
+      # Note: `extraArgs` accepts multiple `|`-separated compiler arguments
 ```
 
-
 ### Using aliases
 
 Avoid the tedium of typing all that out with: